Spray Tank Mixing: Compatibility, Mixing Order and Best Practice
Tank mixing is a routine part of crop protection, allowing compatible products to be applied together where this is appropriate and permitted.
But combining products changes the physical and chemical environment within the spray tank. Product formulation, water quality, mixing order, agitation and compatibility can all affect how the final spray behaves.
Good tank-mixing practice therefore starts with the product label and technical guidance, followed by careful preparation and an understanding of how the products being combined are likely to interact.
What is spray tank mixing?
Tank mixing is the combination of two or more products in the spray tank before application.
This may include combinations of plant protection products, adjuvants, micronutrients or other compatible inputs. Where suitable, combining applications can reduce the number of separate passes required and help simplify field operations.
However, products should only be mixed where their labels and technical guidance allow it and the combination is appropriate for the crop, target and application.
Why tank-mix compatibility matters
Not every product combination will behave in the same way.
Incompatibility can be physical, resulting in settling, separation, thickening, foaming or deposits that may block filters and nozzles. It can also affect product performance or crop safety.
Compatibility should therefore be considered before products are added to the tank, rather than once a problem has occurred.
Product labels remain the first point of reference. Where a tank mix is recommended, specific mixing instructions or restrictions may also be given.
Biostimulants, adjuvants and micronutrients in the tank
Biostimulants, adjuvants and micronutrients can form part of a tank mix, but compatibility should not be assumed simply because individual products are suitable for the crop.
Some biological products may be sensitive to particular conditions or other tank-mix partners, while micronutrient formulations can influence pH, ionic concentration or other characteristics of the spray solution.
Adjuvants can also alter properties such as wetting, spreading, penetration or droplet behaviour, so their inclusion should be based on the requirements of the wider application.
Where compatibility is uncertain, check current product guidance and speak to your Agrii agronomist or technical specialist before mixing.
Check the label before mixing
Plant protection products must be used in accordance with their conditions of authorisation and label instructions.
Where products are being tank mixed, check:
- whether the combination is permitted or recommended;
- any crop or growth-stage restrictions;
- the required mixing order;
- water-volume requirements;
- agitation requirements;
- adjuvant requirements or restrictions; and
- any additional environmental or operator precautions.
HSE guidance also advises adding products individually in the order recommended on the product labels and following any specific instructions on water volume and agitation.
Mixing order
The correct sequence helps products disperse properly and reduces the risk of physical incompatibility.
Always follow product-specific label instructions first. Where no specific sequence is given, general guidance is to add formulations progressively according to their formulation type.
HSE guidance gives the following general order:
- water-soluble bags;
- water-dispersible or soluble granules;
- wettable or soluble powders;
- suspension concentrates;
- emulsifiable concentrates or oil-in-water emulsions; and
- adjuvants.
Agitation should be maintained as required throughout mixing and application.
Water quality and tank mixing
The water used to prepare the spray can influence the behaviour of some products.
Factors such as hardness, pH, temperature and dissolved minerals may affect formulation stability or the performance of certain active ingredients and micronutrients.
Where water quality is known to be an issue, appropriate conditioning may be useful, but the need for treatment depends on the chemistry and the water source.
Water conditioners should therefore be selected for a defined purpose rather than added routinely.
Using a jar test
A jar test can provide a useful indication of physical compatibility where a mix is not already familiar, although it does not replace product label requirements or technical advice.
Use the same water source and relative product concentrations intended for the spray tank and add products in the proposed mixing order.
Signs of poor physical compatibility may include:
- persistent settling;
- layering or separation;
- flakes, crystals or lumps;
- excessive foaming;
- gel formation; or
- material adhering to the container.
If the mix shows signs of incompatibility, do not assume that additional agitation or another adjuvant will solve the problem. Check the product guidance before proceeding.
Agitation and filling
Good agitation helps keep products evenly dispersed in the spray solution.
Begin with an appropriate volume of clean water and maintain agitation as products are introduced according to their formulation and label instructions.
Allow each product sufficient time to disperse before adding the next. Adding several products together too quickly can increase the risk of incomplete dispersion, deposits or instability.
Cleaning spraying equipment
Thorough cleaning is important when changing products or crops, particularly where small residues could damage a following crop.
Cleaning requirements vary between products, so always follow the individual product label and sprayer manufacturer guidance.
This may include rinsing the tank and lines, circulating an appropriate cleaning solution, cleaning filters and nozzles separately, and completing further rinses before the equipment is used again.
Avoid relying on a single generic cleaning product or procedure for every pesticide, as different formulations and active ingredients may require different approaches.
Common tank-mixing problems
Settling and separation
Poor dispersion or incompatible formulations may result in products settling out or separating within the tank.
This can lead to uneven application and deposits within pumps, filters, hoses or nozzles.
Foaming
Some formulations and adjuvants may increase foaming, particularly where agitation is high or the tank is filled too quickly.
Excessive foam can make accurate filling difficult and may indicate that the mixing process needs to be adjusted.
Blocked filters or nozzles
Undispersed granules, precipitates or residues can restrict filters and nozzles, affecting spray output and distribution.
Correct mixing order, adequate water volume and sufficient agitation can help reduce this risk.
Changes in spray behaviour
Adding products to the tank can alter physical properties of the spray solution and, in some cases, affect droplet formation, coverage or drift potential.
The final application should therefore still be considered in relation to nozzle choice, spray quality, boom height, weather and the target being treated.
Tank mixing should support the application
The aim of a tank mix is not simply to combine as many products as possible into one application.
Each component should have a clear purpose, be appropriate at the same timing and be compatible with the other products in the tank.
Where timings or agronomic requirements differ, separate applications may be the better option.
Speak to your Agrii agronomist
Tank-mix decisions can become increasingly complex as crop protection products, adjuvants, micronutrients and biological technologies are brought together.
Your Agrii agronomist can help assess product compatibility, application timing and where individual inputs fit within the wider crop programme.
Disclaimer:
The above content is for informational purposes only and does not constitute agronomic advice. The subject of effective pest and disease management is vast and contains many variables which cannot be fully addressed in this space. Always seek professional advice.